Hydroforming flush system

ABSTRACT

A hydroforming assembly has a plurality of die structures that are mounted on a press for reciprocating movement between open and closed conditions. The die structures have cooperating die surfaces defining a die cavity when in the closed condition and receive a metallic tube blank when in the open conditions. A hydroforming fluid supply system has tube-end engaging structures that are movable to selectively and sealingly engage opposite ends of the tube blank. The hydroforming fluid supply system provides pressurized fluid into an interior of the tube blank in order to expand the tube blank outwardly into conformity with the die cavity. A punch extends within a passage of at least one of the die structures. The punch is movable between retracted and extended positions. A punch driving assembly drives the punch between the retracted and extended positions to punch a hole into the expanded tube blank. A flushing system communicates with the die cavity providing a flushing fluid flow through the interior of the expanded tube blank.

This application is the National Phase of International ApplicationPCT/CA01/00164 filed Feb. 13, 2001 which designated the U.S. Thisapplication is also based on U.S. Provisional Application Ser. No.60/183,783, filed on Feb. 22, 2000, the entire contents of which arehereby incorporated herein by reference thereto.

FIELD OF INVENTION

This invention relates to a system for flushing hydroformed parts toremove debris from inside the part.

BACKGROUND OF THE INVENTION

In recent years, hydroforming technologies have become more and moreimportant in manufacturing, particularly in the automotive industry. Inone application of hydroforming, a tubular metal blank (usually steel)is placed in a die cavity. The opposite ends of the tube are sealed by apair of hydraulic rams having central ports through which extremely highpressure fluid is injected into the tube. The high pressure fluidexpands the tube into conformity with the surfaces defining the cavity.As a result of this hydroforming process, high strength parts can bemade into complex tubular shapes that could otherwise not be achieved inany practical economic fashion. Such hydroforming processes aredisclosed in U.S. Pat. Nos. 4,567,743; 5,070,717; 5,107,693; 5,233,854;5,239,852; 5,333,755; and 5,339,667.

In even more advanced forms of hydroforming, the hydraulic rams areforced inwardly toward one another to create metal flow within the tubeas the tube is being expanded in order to maintain the wall thickness ofthe tube within a predetermined range throughout the expansion process.Such hydroforming processes are disclosed in U.S. Pat. Nos. 5,718,048;5,855,394; 5,899,498; 5,979,201; and 5,987,950.

For certain applications, it is desirable to produce a finished partthat has a plurality of holes therein that can be used to mount othercomponents. For example, in the automotive industry it is known tohydroform a tubular blank in order to form an engine cradle assemblyused to mount an automotive engine. The finished tubular part must beprovided with holes to enable fasteners to pass therethrough formounting engine mounting brackets and the like. To facilitate theprovision of holes in the part, it is known to perform a hole piercingoperation in the hydroforming die itself. Typically, a hole is punchedthrough the tube while under pressure. In one method, the portion of thetube cut out by the punch (sometimes referred to as the “slug”) has anedge portion thereof left connected to the tube, depending into thetube. This is problematic because it adds unnecessary weight to thepart, which is always a concern in the automotive industry. In anothermethod, after the hole is formed, the punch is withdrawn out of thetube, and formed by the punch is maintained in engagement with the punchunder the force of fluid pressure as the punch is withdrawn from thetube. The slug is then flushed by fluid to a scrap collector. One suchtypical operation is disclosed by U.S. Pat. No. 5,816,089. One problemassociated with the aforementioned technique is that on occasion theslug does not exactly align with the hole it came from as it iswithdrawn and may fall into the tube. It must then be retrieved by othermeans.

SUMMARY OF THE INVENTION

It is an object of the present invention to a system for removing scrapfrom an interior of a hydroformed part.

Accordingly, the present invention provides a hydroforming assembly thathas a plurality of die structures mounted on a press for reciprocatingmovement between open and closed conditions. The die structures havecooperating die surfaces defining a die cavity when in the closedcondition and receive a metallic tube blank when in the open condition.A hydroforming fluid supply system has tube-end engaging structures thatare movable to selectively and sealingly engage opposite ends of thetube blank. The hydroforming fluid supply system provides pressurizedfluid into an interior of the tube blank in order to expand the tubeblank outwardly into conformity with the die cavity. A punch extendswithin a passage of at least one of the die structures. The punch ismovable between retracted and extended positions. A punch drivingassembly drives the punch between the retracted and extended positionsto punch a hole into the expanded tube blank. A flushing systemcommunicates with the die cavity providing a flushing fluid flow throughthe interior of the tube blank.

According to another aspect of the invention, there is provided a methodof forming a hole in a hydroformed metallic tube blank and removing apunched scrap therefrom. A plurality of die structures is provided on apress for reciprocating movement between open and closed conditions. Thedie structures have cooperating die surfaces defining a die cavity whenin the closed condition. The die structures are provided in the opencondition. A metallic tube blank is placed into the die cavity. The diestructures are closed. An interior of the tube blank is pressurized witha fluid so as to expand the tube blank into conformity with the diecavity and thus form an expanded tube blank. A punch is forced throughthe expanded tube blank so as to punch a hole therein. The interior ofthe expanded tube blank is depressurized. Fluid is flowed through theexpanded tube blank so as to flush a punched portion of expanded tubeblank out from the interior thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross sectional view of the hydroforming apparatushaving an in-die hydropiercing, and slug disengaging system inaccordance with the principles of the present invention, and showing atubular metallic blank inserted into the hydroforming apparatus inpreparation for hydroforming;

FIG. 2 is similar to FIG. 1, but shows the expanded metallic tube afterhydroforming;

FIG. 3 is an enlarged partial view of the hydroforming apparatus shownin FIG. 2 providing a detailed view of a hydropiercing punch assemblywith the punch in the retracted position;

FIG. 4 is similar to FIG. 2, but shows the punch in its extendedposition after punching a hole into the expanded metallic tube;

FIG. 5 is an enlarged partial view similar to FIG. 3, but showing thepunch in an extended position after punching a hole into the expandedmetallic tube; and,

FIG. 6 is similar to FIG. 4, but showing a punched slug being flushedout of the expanded metallic tube.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now more particularly to the drawings, there is shown thereinin FIG. 1 a schematic cross-section view of a hydroforming apparatusgenerally indicated at 10, which embodies the principles of the presentinvention. The hydroforming apparatus 10 includes a hydroforming press,generally indicated at 12, with an upper support structure 14, a lowersupport structure 16, and vertical support structures 18. Thehydroforming apparatus 10 is equipped with cooperating die structures,which may include an upper die structure 20, and a lower die structure21. The upper die structure 20 can be raised and lowered so that the diestructures 20, 21 are moveable between open and closed positions. Thedie structures 20, 21 are shown in the closed position in FIG. 1. Thedies 20, 21 provide die surfaces 22, defining a sealed die cavity 23when the dies 20, 21 are in the closed position. The shape and size ofthe die cavity 23 is configured to form the desired shape and size ofthe part to be hydroformed. FIG. 1 shows a tubular metal blank 24, whichhas been placed into the die cavity 23 to be hydroformed. The oppositeends of the tubular metal blank 24 are sealingly engaged by a pair ofhydraulic tube-end engaging structures, or “hydraulic rams” 25, whichare movable into varied positions driven by a hydraulic actuator 26.Each ram 25 has a cental port 27 through which extremely high pressurehydroforming fluid (e.g., approximately 10,000 atms.) is injected intothe tubular metal blank 24.

Incorporated into at least one of the die structures 20, 21, is areciprocating hydropiercing punch assembly, generally indicated at 50,which is shown in detail in FIG. 3.

The hydroforming apparatus 10 is equipped with a flushing fluid system,generally indicated at 30, which communicates with the die cavity 23.The flushing fluid system 30 is used to remove at least one punched outportion, or “slug” 86, of the expanded metallic tube 24, (as shown inFIG. 4). The flushing fluid system 30 includes a flushing fluid inletport 32 which is located at on e end of the die cavity 23 and a flushingfluid outlet port 33 which is located at the opposite end of the diecavity 23. Preferably, both of these ports 32 and 33 are formed into thelower die structure 21 as shown. The flushing fluid system 30 preferablyincludes a scrap separator generally indicated at 34 with a mesh orscreen 36. Also, the flushing fluid system preferably includes a fluidreservoir 38 which can be used for storing and/or recycling the flushingfluid, if desired. The flushing fluid system 30 also includes connectingplumbing lines 42 and a circulator 40 for circulating the flushing fluidthrough the flushing fluid system 30.

Referring now to FIG. 3, the hydropiercing punch assembly 50, is shownin greater detail. The punch assembly 50 is used to punch a hole 84 (asshown in FIG. 4) into the expanded metallic tube 24. Any number ofsimilarly designed punch assembly 50 may be incorporated into one ormore of the die structure(s) 20, 21. The punch assembly 50 includes apunch receiving passage 51 that is incorporated into the diestructure(s) and through which a punch 52 may be moved between aretracted and an extended position. The punch 52 is movable in slidable,sealed relation with respect to the passage 51 by virtue of an annularseal member 53 therebetween. The punch assembly 50 includes a punchdriver assembly generally indicated at 54, which is used to drive thepunch 52 between the retracted and extended positions. In the retractedposition, the distal end surface 55 of the punch 52 is flush with thedie surfaces 22, and helps to define the die cavity 23. The punch driverassembly 54 includes a punch driver 56, which may be a hydrauliccylinder, that is connected to a punch piston 58. The proximal end 59 ofthe punch 52 is secured to and connected to the punch piston 58. Thepunch piston 58 is movable between a retracted and an extended position.The punch 52 traverses through an opening 62 in a punch driver housing60 in slidable relation with respect to the opening 62.

The flushing fluid system 30 may include a slug disengaging system,generally indicated at 70, which can provide a means of disengaging theslug 86 from the end working surface 55 of the punch 52. At least one ofthe die structures 20, 21 is mounted to a slug disengaging fluidbulkhead 72. A peripheral seal 74 between the die structure 20, 21 andthe bulkhead 72 surrounds the slug disengaging system 70 so that theslug disengaging system 70 is sealed from atmosphere and can bepressurized with slug disengaging fluid. The slug disengaging system 70includes a slug disengaging fluid input port 76 which is located on theslug disengaging fluid bulkhead 72. The slug disengaging fluid inputport 76 can be connected to any suitable high pressure pump to providepressurized slug disengaging fluid to the slug disengaging system 70.The slug disengaging fluid input port 76 is connected to a slugdisengaging fluid passageway 78 which can be common to several punchassemblies 50. The passageway 78 can be any suitably sized groove formedinto the die structure(s) 20, 21. The passageway 78 communicates with aslug disengaging fluid pressure chamber 79 that can be formed into thedie structure(s) 20, 21. The punch 52 includes a slug disengaging fluidport 80 which traverses longitudinally through the punch 52. The slugdisengaging fluid port 80 originates at a slug disengaging fluid inlet82 located on the side of the punch 52 and terminates with an outlet 83at the punch working surface 55. The slug disengaging fluid inlet 82 canbe located so as to communicate with the slug disengaging fluid pressurechamber 79 when the punch 52 is in the extended position so that theslug disengaging fluid port 80 can be pressurized with slug disengagingfluid as desired.

Operation of the hydroforming apparatus 10 will now be described.Referring to FIG. 2, the metallic tube 24 is expanded under hydroformingfluid pressure into conformity with the inner surfaces 22 of the diecavity 23 and into engagement with the working surface 55 of the punch52 which is in the retracted position. So as to maintain predeterminedwall thickness of the expanded metallic tube 24, the hydraulic rams 25are forced inwardly toward one another to create metal flow within thetube 24 as the tube 24 is being expanded.

In FIG. 4, the punch driver or cylinder 56 is actuated and drives thepunch piston 58 into the extended position. This action drives the punch52 from the retracted position to the extended position after themetallic tube 24 has been expanded into conformity with the die surfaces22, thus forcing the punch 52 through the expanded metallic tube 24 soas to punch a hole 84 in the expanded metallic tube 24, and so as toform the slug 86. Hydroforming fluid is maintained under high pressurewithin the expanded metallic tube 24 to provide interior support to thetube 24 during the hole punching sequence in order to preventdeformation of the expanded metallic tube 24 by the punch 52 at areasadjacent to the punched hole 84. The die structures 20, 21 aremaintained in the closed position, and the expanded metallic tube 24maintains engagement with the surfaces 22 of the die cavity 23. In theextended position, the punch 52 serves to seal the hole 84 that has beenpunched into the tube 24 thus aiding to maintain fluid in the tube 24 soas to inhibit the escape of fluid from the tube 24 during a subsequentslug flushing operation.

FIG. 5 shows the punch 52 in the extended position in greater detail.The slug disengaging fluid inlet 82 communicates with the slugdisengaging fluid pressure chamber 79 thus permitting flow of the slugdisengaging fluid through the slug disengaging fluid port 80.

Referring now to FIG. 6, at least one of the hydraulic rams 25, that is,at least the ram adjacent to the outlet port 33, but preferably bothrams, is movable out of sealed engagement with the end(s) of theexpanded metallic tube 24, thus permitting the hydroforming fluid in thetube 24 to become depressurized. The hydraulic rams 25 are nowpositioned so as to facilitate flow of flushing fluid and removal of theslug 86 from the tube 24. The die structures 20, 21 remain in the closedposition and the flushing fluid system 30 communicates with the diecavity 23 to provide flow of flushing fluid to the interior of theexpanded metallic tube 24.

Typically, the slug 86 may remain engaged to the end working surface 55of the punch 52. If this is the case, the invention provides variousmeans for disengaging the slug 86 from the end working surface 55 of thepunch 52.

In one embodiment, the slug 86 can be forcibly disengaged from the endsurface 55 of the punch 52 by pressurization of the slug disengagingsystem 70 which forces fluid through the fluid port 80 and detaches theslug 86 from the working surface 55 of the punch 52. Alternatively, thepunch driver 56 may be used to rapidly reciprocate the punch 52 todisengage the slug 86 from the working surface 55 of the punch 52.

In yet another embodiment, the slug 86 can be forcibly disengaged fromthe end working surface 55 of the punch 52 solely by rapid flow offlushing fluid through the tube 24 as provided by the flushing fluidsystem 30.

The flushing fluid circulator 40 and the connecting plumbing lines 42provide sufficiently high flow rate of flushing fluid so as to flush thedetached metal slug 86 through the expanded metallic tube 24 and toremove the slug 86 from the tube 24. The flushing fluid flows throughthe inlet port 32, passes through the tube 24 and carries the slug 86out through the opposite end of the tube 24 and out through the outletport 33. The outlet port 33 and the connecting plumbing lines 42 aresuitably sized with wide enough inner diameter so as to permit theunobstructed flow of the flushing fluid and the slug 86 out of the die21. Once the metal slug 86 is removed from the die 21, the slug 86 canbe separated from the flushing fluid by the mesh or screen 36 in thescrap separator 34, and the fluid can be recovered into the fluidreservoir 38. During the flushing fluid sequence, the punch 52 ismaintained in the extended position so as to prevent leakage of flushingfluid through the punched out hole 84 in the tube 24.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not limiting in character, it being understood that thepreferred embodiment has been shown and described and that all changesand modifications that come within the scope of the appended claims areto be protected.

What is claimed is:
 1. A hydroforming assembly, comprising: a pluralityof die structures mountable on a press for reciprocating movementbetween open and closed conditions, said die structures havingcooperating die surfaces defining a die cavity when in the closedcondition, said die structures receiving a metallic tube blank when inthe open condition; a hydroforming fluid supply system having tube-endengaging structures that are movable to selectively and sealingly engageopposite ends of said tube blank, said hydroforming fluid supply systemproviding pressurized fluid into an interior of said tube blank in orderto expand the tube blank outwardly into conformity with said die cavityinto an expanded condition, a punch extending within a passage of atleast one of said die structures, said punch movable between retractedand extended positions; a punch driving assembly operably connected withsaid punch to drive said punch between said retracted and extendedpositions to punch a hole into said tube blank after said tube blank hasbeen expanded into said expanded condition; and a flushing systemcommunicating with said die cavity providing a flushing fluid flowthrough the interior of said tube blank.
 2. A hydroforming assembly asclaimed in claim 1, wherein said punch has a working surface, saidworking surface being co-planar with a die surface of said die cavitywhen said punch is in said retracted position, and said working surfaceextends into said die cavity when in said extended position.
 3. Ahydroforming assembly according to claim 2, wherein the punch has afluid passageway in communication with the working surface of the punch,the fluid passageway communicating with a source of pressurized fluidwhich can be expelled through said fluid passageway so as to urge apunched portion of said tube blank away from said working surface of thepunch.
 4. A hydroforming assembly as claimed in claim 3, wherein saidfluid passageway communicates with said source of pressurized fluid whensaid punch is in said extended position.
 5. A hydroforming assembly asclaimed in claim 4, wherein said punch driving assembly includes ahousing having an opening and said punch extends through said opening.6. A hydroforming assembly as claimed in claim 5, wherein an interior ofsaid housing is isolated from said source of pressurized fluid and saidfluid passageway has an inlet positioned such that the inletcommunicates with the interior of the housing when the punch is in theretracted position and the inlet is positioned out of the housing whenthe punch is in the extended position.
 7. A hydroforming assembly asclaimed in claim 6, wherein said pressurized fluid is a gas.
 8. Ahydroforming assembly according to claim 1, wherein said punch isretained in said extended position during said flushing fluid flow.
 9. Ahydroforming assembly according to claim 1, wherein said punch isreciprocated during said flushing fluid flow.
 10. A hydroformingassembly according to claim 1, wherein said tube-end engaging structuresretract from engagement with ends of said tube blank to opencommunication of said flushing system with the interior of the tubeblank.
 11. A hydroforming assembly according to claim 1 wherein saidflushing system comprises, a scrap separator receiving said flushingfluid flow from said die cavity, a fluid reservoir providing a source offluid for said flushing fluid flow and a circulator for effecting saidflushing flow.
 12. A method of forming a hole in a hydroformed metallictube blank and removing a punched scrap therefrom, said methodcomprising: providing a plurality of die structures mounted on a pressproviding reciprocating movement between open and closed conditions,said die structures having cooperating die surfaces defining a diecavity when in the closed condition, said die structures being in theopen condition; placing a metallic tube blank into said die cavity;closing the die structures; pressurizing an interior of said tube blankso as to expand said tube blank into conformity with said die cavity andthus form an expanded tube blank; forcing a punch through said tubeblank so as to punch a hole in said expanded tube blank; depressurizingthe interior of said expanded tube blank; and flushing fluid throughsaid expanded tube blank so as to flush a punched portion of expandedtube blank out from the interior of said expanded tube blank.
 13. Amethod according to claim 12, wherein the punch has a fluid passagewayin communication with a working surface of the punch, and the methodincludes a step of providing pressurized fluid through said fluidpassageway so as to urge a punched portion of said expanded tube blankaway from said working surface of the punch.
 14. A method according toclaim 12, wherein method includes a step of reciprocating said punchduring said step of flushing fluid.
 15. A method according to claim 12,wherein said step of depressurizing includes a step of openingcommunication of said flushing system with the interior of the expandedtube blank.
 16. A method according to claim 12, wherein said punch isretained in an extended position extending into the interior of saidexpanded tubular blank during said step of flushing fluid.